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Intergalactic space travel

by Kenneth w
Tags: intergalactic, space, travel
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Kenneth w
#1
Aug10-11, 12:43 AM
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How fast must we go to travel to another galaxy?
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zhermes
#2
Aug10-11, 01:57 AM
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Depends on how fast you want to get there.
Ryan_m_b
#3
Aug10-11, 04:07 AM
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That obviously depends on a whole host of other things;

First you have to build a ship capable of sustaining a stable ecology indefinitely (exception to this is if you plan to have to ship come back to Earth, in which case it has to be capable of maintaining an environment for the duration of the mission).

Then you have to make an industrial complex so that the ship can maintain it-(probably massive)-self. This complex is going to have to be a highly versatile closed system, kind of like rolling up one of each type of factory and redesigning them to be near 100% recyclable.

After that you have to pack aboard enough people to maintain the ship and a society within, also you need enough people to fill every specialised type of labour which is going to be measured in the millions. Obviously you are going to have to design a social and political system capable of lasting a hell of a long time (human institutions don't have a good track record of this) with absolutely no failure modes. An economic collapse within a ship that leads to the atmosphere generator engineers taking the whole ship hostage to feed their families would not be a good thing.

Lastly you are ultimately limited by the speed of light, if you had good enough technology you could take advantage of time dilation but this is still an undertaking that would require almost miraculous scientific, technological and social breakthroughs.

Octonion
#4
Aug10-11, 09:06 AM
P: 11
Intergalactic space travel

ORRRR you can do some research on the potentiality of a new form of travel where one simply contract the space-time between you and the galaxy over and over again until you are extremely close to it. Miguel Alcubierre wrote a paper on this in 1994 and recently there was proof that such contractions could occur on small scales at MIT..i believe..it could have been somewhere else. But luckily, space-time can be contracted at speeds far exceeding that of the speed of light its just a matter of waiting thousands of years until such technology exists. MY prediction is that we will not travel to other galaxies while the speed of light is the maximum limit for our travel speed.
Octonion
#5
Aug10-11, 09:09 AM
P: 11
Here's an updated paper submitted in 2000 http://arxiv.org/pdf/gr-qc/0009013v1
Cosmo Novice
#6
Aug10-11, 09:50 AM
P: 366
Quote Quote by Octonion View Post
ORRRR you can do some research on the potentiality of a new form of travel where one simply contract the space-time between you and the galaxy over and over again until you are extremely close to it. Miguel Alcubierre wrote a paper on this in 1994 and recently there was proof that such contractions could occur on small scales at MIT..i believe..it could have been somewhere else. But luckily, space-time can be contracted at speeds far exceeding that of the speed of light its just a matter of waiting thousands of years until such technology exists. MY prediction is that we will not travel to other galaxies while the speed of light is the maximum limit for our travel speed.
Assuming such technology will ever exist is rather naive. The Alcubierre Drive does not qualify what I would call as a "paper", it is a thought experiment only. It has no more value as a theory than an actual FTL drive would have - both have no value in real science, they just show potential operating mechanisms; assuming the potential technology can exist and we have the potential to achieve such technology on a technical, social, economic scale and accepting the limitation that exotic matter may not exist! Rather large assumptions!

This paper has popped up a lot on these forums unfortunately.
Ryan_m_b
#7
Aug10-11, 11:41 AM
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Quote Quote by Octonion View Post
ORRRR you can do some research on the potentiality of a new form of travel where one simply contract the space-time between you and the galaxy over and over again until you are extremely close to it. Miguel Alcubierre wrote a paper on this in 1994 and recently there was proof that such contractions could occur on small scales at MIT..i believe..it could have been somewhere else. But luckily, space-time can be contracted at speeds far exceeding that of the speed of light its just a matter of waiting thousands of years until such technology exists. MY prediction is that we will not travel to other galaxies while the speed of light is the maximum limit for our travel speed.
Quote Quote by Octonion View Post
Here's an updated paper submitted in 2000 http://arxiv.org/pdf/gr-qc/0009013v1
There has been no work that I am aware of that has shown the Warp drive to be anything but a theoretical proposal requiring types of matter that may not even exist (If you have a link from MIT you really should post it as anything showing exotic matter would be groundbreaking).I've discussed this issue before so rather than type it again I'm just going to quote myself;
Quote Quote by ryan_m_b View Post
To accelerate to the speed of light would require either infinite energy or infinite time so yes, it is the limit. There are speculative proposals to get around this; wormholes and warp drives.

It may be possible to create traversable wormholes to allow short cuts in space. However this requires exotic matter that may not even exist and you would still have to drag one of the wormholes to your destination of choice slower than light (you also have the tricky problem that you have now created a potential time machine but this could be resolved if Visser collapse or some other CPC held true).

On the subject of warp drives this paper which is further discussed in this paper proposes ways of getting around the horrendous energy requirements outlined in this paper. The "trick" is to change the warp bubble so that it's exterior radius is microscopic yet the interior radius is large enough to accommodate your vehicle (essentially making a warp bubble that's bigger on the inside than on the out). Apparently this would greatly shrink the amount of energy needed to manageable levels. They don't outline how exactly a shell could be build around a ship in such a fashion nor how the ship could leave.

However neither of these approaches fixes the other problems of a warp bubble such as requiring the construction of an exotic matter shell, superluminal signalling to steer/control the bubble and the huge amount of radiation a warp drive subjects you to. There are some interesting (but technical) objections in this paper that apparently show that a warp drive would only be capable of very low velocities as well as highlighting other problems.

So without exotic matter that may not even exist we are stuck to trying to make slower than light vehicles. To make an interstellar vehicle would be fantastically complex though requiring horrific amounts of energy (even if we used an antimatter rocket we would need potentially thousands-millions of tonnes for a high fraction of c.) as well as a thorough understanding of ecology so as to make a stable environment in a closed system to keep the occupants alive.
jnorman
#8
Aug10-11, 03:30 PM
P: 308
anywhere near the speed of light will work pretty well. if you can get your spaceship to 0.99999C, you can travel to another galaxy within a reasonable amount of time, according to your ship's clocks (at that kind of speed, your ship will travel around 10LY per year of your clock time). however, the amount of time which passes on earth during your trip will be ENORMOUS.
Cosmo Novice
#9
Aug10-11, 04:55 PM
P: 366
Quote Quote by jnorman View Post
anywhere near the speed of light will work pretty well. if you can get your spaceship to 0.99999C, you can travel to another galaxy within a reasonable amount of time, according to your ship's clocks (at that kind of speed, your ship will travel around 10LY per year of your clock time). however, the amount of time which passes on earth during your trip will be ENORMOUS.
Yes but if you even touch 1gram of matter at close to c the energy release is nuclear equivalent...
Kenneth w
#10
Aug10-11, 11:46 PM
P: 3
Hmm, Andromeda is 2,000,000+ lys away. At c, it would take 2mil years to get there. To do it in ten years would take a speed of millions of times c. Lets talk energy consumption, photons travel at c, why don't they consume infinite energy? Photons do have mass..very little, but they do have some and it takes energy to energize them to c. Where does that energy come from? I don't know, but I don't think they consume infinite energy. Who has proven that time dilation is directly porportional to speed? There may be a limit, if so, all current math concerning it may be flawed. I don't believe that the physics and the math concerning FTL travel has been discovered yet.
Ryan_m_b
#11
Aug11-11, 03:35 AM
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Quote Quote by Kenneth w View Post
Hmm, Andromeda is 2,000,000+ lys away. At c, it would take 2mil years to get there. To do it in ten years would take a speed of millions of times c. Lets talk energy consumption, photons travel at c, why don't they consume infinite energy? Photons do have mass..very little, but they do have some and it takes energy to energize them to c. Where does that energy come from? I don't know, but I don't think they consume infinite energy. Who has proven that time dilation is directly porportional to speed? There may be a limit, if so, all current math concerning it may be flawed. I don't believe that the physics and the math concerning FTL travel has been discovered yet.
Time dilation is indeed well established.
http://en.wikipedia.org/wiki/Time_dilation

Photons don't have mass in the conventional sense, just because photons can impart momentum doesn't mean they have mass.
http://en.wikipedia.org/wiki/Photon

Faster than light travel is not possible. Aside from the need for infinite energy the only speculative proposals are most likely impossible (as I discussed above). You would also now violate causality which would produce a whole bunch more problems.
http://en.wikipedia.org/wiki/Causality_(physics)
Cosmo Novice
#12
Aug11-11, 03:36 AM
P: 366
Quote Quote by Kenneth w View Post
Lets talk energy consumption, photons travel at c, why don't they consume infinite energy? Photons do have mass..very little, but they do have some and it takes energy to energize them to c.
Ok. Photons dont consume energy because they are called bosons - which means they are massless particles, their mass is considered relativistic and is momentum mass - not mass in the normally considered sense.

Quote Quote by Kenneth w View Post
Who has proven that time dilation is directly porportional to speed?
The EFE proves this - it is the second postulate of SR and has been proved experimentally.

Quote Quote by Kenneth w View Post
Hmm, Andromeda is 2,000,000+ lys away. At c, it would take 2mil years to get there
It would take approx. 2mil years from the FoR of the external observer on earth. For the crew of HMS Andromeda they would get their in a very reasonable time due to the relativistic effects of time dilation.

Quote Quote by Kenneth w View Post
There may be a limit, if so, all current math concerning it may be flawed. I don't believe that the physics and the math concerning FTL travel has been discovered yet.
The math on FTL is pretty clear - its not physically possible. As you accelerate towards c the energy required to continue accelerating approaches infinity, therefore c is not attainable by anything with rest mass.
moejoe15
#13
Aug11-11, 09:51 PM
P: 39
A one way trip at even a small percentage of the speed of light should be possible by technology we will have this century if we had the will. We won't because there will be no return on the investment. Who cares how long it takes? We are already time travelers. We just need to figure out a way to suspend animation. Finding a volunteer will be easy, there are always people willing to explore the unknown.

If we really were an intelligent species, and the only one around, we could spread DNA throughout this galaxy. The speed of light is really only a time limit for expansion of life if we wanted to seed this galaxy. We don't have to send people. We could send just bacteria and let evolution take it's course. Maybe someday in the far future we will see smoke signals from our efforts if we survive, if we don't we would at least know we have sown the seeds.
Lobezno
#14
Aug12-11, 03:57 AM
P: 53
Quote Quote by moejoe15 View Post
If we really were an intelligent species, and the only one around, we could spread DNA throughout this galaxy. The speed of light is really only a time limit for expansion of life if we wanted to seed this galaxy. We don't have to send people. We could send just bacteria and let evolution take it's course. Maybe someday in the far future we will see smoke signals from our efforts if we survive, if we don't we would at least know we have sown the seeds.
That is an interesting proposition, but I'm afraid chances are, we'll be long gone before vaguely sentient beings evolve. In evolution time units, the time that is required for a sizable change in a species, it's just not viable. The Sun will die out before then.
moejoe15
#15
Aug15-11, 03:52 PM
P: 39
It isn't written in stone that our species can't survive longer than the earth or our sun. Even if we can't populate the galaxy ourselves directly the nearer stars may not be out of reach of future technology. Future technology might allow us to spread life advanced enough to bypass much of the evolutionary time required to produce advanced lifeforms. If it turns out life is extremely rare or non-existent I would feel a lot better knowing that our eggs were in more than one basket.
qraal
#16
Aug15-11, 09:31 PM
P: 775
Wait long enough and M31 will come to us.
Chronos
#17
Aug15-11, 10:00 PM
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All of the interstellar/intergalactic travel issues posed here are possible explanations for the Fermi paradox.
edpell
#18
Aug16-11, 09:58 PM
P: 451
Bosons such as pions do have mass. Boson versus fermion refer to there statistics it has nothing to do with their mass.


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